Ceria/zirconia fiberes for use in cigarettes

ABSTRACT

Ceria/zirconia fibres are incorporated into a variety of smokable articles or their separate individual components, in particular, cigarette components such as a cigarette paper/wrapper, tobacco, and/or filter.

FIELD OF THE INVENTION

The invention relates to incorporation of ceria/zirconia fibres into anindividual component of a cigarette, in particular, cigarette componentssuch as a cigarette paper/wrapper, tobacco, and/or filter.

BACKGROUND OF THE INVENTION

Metal oxide catalysts have been incorporated onto the surface of varioustypes of fibres for decomposing various compositions or for purifyingexhaust gases. For example, U.S. Pat. No. 5,094,222 describes a mixtureof ceramic fibres containing an oxidation catalyst for decomposition offats and oils. The ceramic fibres are made from at least one of thefollowing oxides: silicon oxide, zirconium oxide and aluminum oxide andthe oxidation catalyst is selected from at least one of a variety ofmetal oxides. U.S. Pat. No. 5,165,899 describes a porous fibrousstructure for purification of exhaust gases. The fibrous structure ismade of metal alloy fibrils of the MCrAlX type where M is a matrixchosen from iron, and/or nickel and/or cobalt and X is chosen fromzirconium, yttrium, cerium and lanthanum metal.

Several patents refer, more specifically, to various processes formaking metal oxide/zirconium oxide fibres. U.S. Pat. No. 5,468,548describes a process for making reinforced fibres for high temperaturecomposites consisting of a matrix and eutectic fibres dispersed in thematrix. The eutectic fibres can be selected from a series of metaloxides and the reference suggests several optional metal oxidesincluding ceria and zirconia. U.S. Pat. No. 3,891,595 describes theprocess of making friction materials that contain 40-85% of a syntheticinorganic refractory metal oxide fibre and 15-35% of a binder. The metaloxide fibre may contain zirconia and 1-10% of a stabilizer, such asalkaline oxides, yttria and rare earth oxides.

U.S. Pat. Nos. 4,927,622, 5,053,214 and 5,112,781 describe a processthat involves making an aqueous solution of zirconium-based granules anda phase stabilizer (1-35wt %), such as calcium, yttrium, cerium andhafnium oxides, and fiberizing the solution. This particular processinvolves making and drying the zirconium-based granules before makingthe fibre.

U.S. Reissued Pat. No. 35,143 describes a process for making a ceramicfibre that involves mixing crystalline zirconium grains, a zirconiacompound, solvent and a phase stabilizer (more than 0 and up to 20 mol %of the stabilizer).

Although these references disclose various uses of metal oxide/zirconiafibres, none have attempted to specifically combine such fibres withknown cigarette technology.

In the cigarette industry, various attempts have been made toincorporate specific fibres and other additives into cigarettes. Forinstance, U.S. Pat. No. 2,755,207 describes a cigarette paper thatyields a smoke substantially free of obnoxious components. The cigarettepaper is made from cellulosic fibre, which has intimately associatedtherewith a finely divided mineral type siliceous catalyst material andfunctions like a catalyst in modifying the combustion of the paper.

Published International Patent Application WO 99/53778 describes anon-combustible sheet of treatment material for reducing sidestreamsmoke emissions. The sheet is used as a wrap and is applied overconventional cigarette paper of a conventional cigarette. The wrap has avery high porosity to allow the cigarette to burn at or close toconventional free-burn rates while at the same time reduce visiblesidestream smoke emissions. The non-combustible wrap includesnon-combustible ceramic fibres, non-combustible activated carbon fibresas well as other standard materials used in making the wrap. The wrapalso includes zeolites or other similar sorptive materials and an oxygendonor/oxygen storage metal oxide oxidation catalyst. The non-combustiblewrap provides an acceptable degree of sidestream smoke control, however,due to the non-combustible nature of the wrap, a charred tube remains.

U.S. Pat. Nos. 4,433,697 and 4,915,117 describe the incorporation ofceramic fibres in a cigarette paper manufacture. U.S. Pat. No. 4,433,697describes at least 1% by weight of certain ceramic fibres in the paperfurnish in combination with magnesium oxide and/or magnesium hydroxidefillers to reduce visible sidestream smoke emanating from the burningcigarette. The furnish of fibre pulp, ceramic fibres and fillers areused to make a paper sheet on conventional paper making machines. Theceramic fibres are selected from the group consisting of polycrystallinealumina, aluminum-silicate and amorphous alumina. A filler of magnesiumhydroxide or magnesium oxide is used and is coated on or applied to thefibres of the sheet.

U.S. Pat. No. 4,915,117 describes a non-combustible sheet for holdingtobacco. The thin sheet is formed from ceramic materials which uponburning produces no smoke. The ceramic sheet comprises a woven ornon-woven fabric of ceramic fibre or a mixture of paper and ceramicsthermally decomposed at high temperature. The ceramic fibre may beselected from inorganic fibres such as silica fibre, silica-aluminafibre, alumina fibre, zirconia fibre, or alumino borosilicate and glassfibre. The ceramic sheet is formed by binding these materials usinginorganic binders such as silica gel or alumina gel. The fibres arepreferably 1 to 10 micrometers in diameter.

Published International Patent Application WO 02/024005 describes asidestream smoke treatment composition which is particularly adapted toreduced sidestream smoke emissions. The composition comprises an oxygenstorage and donor metal oxide oxidation catalyst and an essentiallynon-combustible finely divided porous adjunct for the catalyst. Ceriumoxide is a particularly preferred oxygen donor material. The porousadjunct is preferably zeolites but also includes zirconia, titania,ceria, alumina, zirconium fibres and milled porous ceramic fibres.

SUMMARY OF THE INVENTION

In one aspect of the present invention, there is provided a cigarettecomprising a tobacco rod, a cigarette paper/wrapper for the tobacco rod,and optionally a filter, wherein at least one of the tobacco rod, thecigarette paper/wrapper and the filter comprise ceria/zirconia fibres.Preferably, the ceria/zirconia fibres contain up to about 50% by weightceria.

In accordance with a preferred aspect of the present invention, thecigarette paper/wrapper comprises porous ceria/zirconia fibres with asurface area greater than about 20 m²/g.

For ease of description, whenever the term cigarette is used, it isunderstood not only to include smokable cigarettes but any form ofwrapped smokable product, such as cigars or the like. Whenever the termcigarette paper/wrapper is used, it is understood to encompasscombustible and non-combustible papers and the like which may be used oncigarettes, cigars and the like. The paper/wrapper may be used as asingle layer of cigarette paper or multiple layers of cigarette paper.The paper/wrapper may be applied as the sole layer of cigarette paper oras a wrap over conventional cigarette paper of a cigarette.

DETAILED DESCRIPTION OF THE INVENTION

Ceria/zirconia fibres are incorporated into an individual component of acigarette, in particular, cigarette components such as a cigarettepaper/wrapper, tobacco, and/or filter. Use of ceria/zirconia fibres incigarettes provides an unexpected benefit of being able to incorporate ahigher concentration of ceria and zirconia into the cigarettepaper/wrapper without sacrificing wet strength as compared to theincorporation of ceria/zirconia particulates.

The present invention incorporates ceria/zirconia fibres, such as thosedescribed in U.S. Pat. Nos. 4,927,622; 5,053,214; 5,112,781; U.S.Reissued Pat. No. 35,143, U.S. application Ser. No. 60/318,614, entitledZirconium/Metal Oxide Fibres, filed Sep. 13, 2001, all of which areherein incorporated by reference, into an individual component of acigarette, more particularly, cigarette components such as cigarettepaper/wrappers, tobacco, and filters.

Representative ceria/zirconia fibres may be made in accordance with oneor more of the following processes.

The ceria/zirconia fibres may be made according to the method describedin U.S. Pat. No. 4,927,622 and its' related patents, U.S. Pat. Nos.5,053,214 and 5,112,781. The method involves combining an aqueoussolution of a zirconium compound, such as zirconium acetate, with ceriumacetate (about 1 to 35% by weight based upon the total weight ofzirconia in solution). The pH of the solution is about 2 to 7. Thesolution is then heated at a temperature below about 180° C. toevaporate the water and produce amorphous zirconium-based granulescontaining ceria. These granules are added to water in a weight ratio ofabout 4:3 and placed on drum rollers to form a viscous solution. Thissolution is fiberized and the resulting fibres are then sintered toyield ceria/zirconia fibres.

The ceria/zirconia fibres may also be made according to the methoddescribed in U.S. application Ser. No. 60/318,614, entitledZirconium/Metal Oxide Fibres, filed Sep. 13, 2001. The ceria/zirconiafibre is made by adding a solution of cerium nitrate to the polymer ofFormula (I). The cerium nitrate solution is made by mixing ceriumcarbonate with nitric acid or by dissolving cerium nitrate in water. Thesolution is then admixed with a colloidal dispersion comprising theamorphous zirconium polymer of the formula:[Zr₄(OH)₁₂(X)₂(H₂O)₄]_(n)(X)_(2n).2nH₂ 0  (I)

wherein X is preferably NO₃ and n is a whole number. The mixing is doneat approximately 15 to 25° C. The mixed colloidal dispersion isfiberized by conventional drawing techniques such as pulling or drawing,centrifugal spinning, nozzle injection or blow spinning. Usually aspinning aid is utilized in order for the dispersion to fibreizeproperly. Suitable spinning aids include polyvinyl pyrrolidone,polyethylene oxide, polyvinylalcohol, polyurethane, polyacrylic acidsalt, polyacrylamide and polyvinylmethyl ether. The ceria/zirconiafibres of this method usually have less than 15% non-fibrous material.

The ceria/zirconia fibres may be made according to the method describedin U.S. Reissued Pat. No. 35,143 (assigned to 3M). The method involvescombining an aqueous solution of a zirconium compound (ie. zirconiumacetate; about 20 to 80% by weight based upon the total weight ofzirconia in solution), ceria (up to about 20% by weight based upon thetotal weight of zirconia in solution), an organic polymer (i.e.polyvinylpyrrolidone; about 0 to about 50% by weight based upon thetotal weight of zirconia in solution) and a crystalline, colloidalzirconia sol (ie. Nyacol™ Zr 100/20; about 20 to about 80% by weightbased upon the total weight of zirconia in solution). This solution wasfiltered and concentrated to a viscosity of about 80-90 PaSec. Theviscous solution was extruded and the resulting fibres sintered to yieldceria/zirconia fibres. Depending on the use, these ceria/zirconia fibresmay be continuous or discontinuous and may have a high surface area (inthe range of 1 to 200 m²/g) or low surface area (less than 1 m²/g). Itis preferred that, during the sintering step, the firing rate does notexceed 10° C./min until a temperature of about 500° C. is attained. Oncethe fibres have been fired to 500° C., they may be very rapidly heated(i.e. 100° C./min) to higher temperatures. The fibres, when fired toless than about 1100° C., contain a high porosity and consequently ahigh surface area. As the fibres are fired to higher temperatures (about1100° C. to about 1400° C.), their porosity and surface area decreasesand the fibres possess higher tensile strengths.

Typically, the ceria/zirconia fibres used in the present inventioncontain up to about 50% by weight ceria and, more preferably, up toabout 25% by weight. These fibres usually have a diameter greater than 5micrometers, preferably in the range of about 8 to about 25 micrometers.The tensile strength of these fibres is, typically, about 1 to about 80g/mm, preferably in the range of about 1 to about 50 g/mm.

It is understood that as the porosity of the ceria/zirconia fibresincreases their structural strength may decrease. There are severalapplications for these fibres in cigarettes where the porosity of thechosen fibre compliments its' use. For example, fibres for structuraland reinforcement applications would have lower porosity, whereas fibresfor reducing sidestream smoke would have higher porosity. Preferably,the ceria/zirconia fibres used for reducing sidestream smoke are porous,that is, the fibres have a high surface area, particularly in the rangeof about 1 to about 200 m²/g, preferably greater than about 20 m²/g. Theceria/zirconia fibres having a surface area less than about 1 m²/g arebetter suited for reinforcement applications.

The ceria/zirconia fibres may be used as follows: a cigarettepaper/wrapper may be made from the ceria/zirconia fibres and wrappedover, and in substantial contact, with a conventional cigarette paper ofa cigarette or a tobacco rod of a cigarette; a tube may be made from theceria/zirconia fibres and placed on and in substantial contact with aconventional cigarette paper of a cigarette or a tobacco rod; and acigarette paper/wrapper may comprise conventional cigarettepaper/wrapper fibres (i.e. cellulosic fibres) and ceria/zirconia fibres.

The paper/wrappers described herein may be used as a single layer ofcigarette paper/wrapper or multiple layers of cigarette paper/wrappers.

Reference to a normal or conventional cigarette, cigarette paper, orcigarette paper/wrapper fibres implies commercially availablecigarettes, typically, having a porosity in the range of about 5 toabout 50 Coresta units, sometimes as high as 110 to 120 Coresta units,and a conventional free-burn rate of about 3 to about 5 mm/min givenconventional tobacco densities of about 0.20 to about 0.26 g/cc.Conventional cigarettes, at least in North America, have a circumferenceof about 20 to 30 mm, usually about 23 to 27 mm and a tobacco rod lengthof at least about 30 mm and preferably of about 55 mm, about 64 mm andabout 74 mm, which has acceptable draw resistance.

When the ceria/zirconia fibre is wrapped over and in substantial contactwith cigarette paper of a cigarette or the ceria/zirconia fibre tube isplaced on and in substantial contact with cigarette paper of acigarette, this arrangement permits the use of a conventional cigaretteand when smoked, burns at conventional free-burn rates. The tube may bedesigned to reduce sidestream smoke such as described in applicant'sInternational Application WO 98/16125. The ceria/zirconia fibrepaper/wrapper works at very low porosities (refers to porosity of paperitself, not porosity of fibre) of about 0.5 through to very highporosity of about 10,000 Coresta units. Preferred porosities are usuallyless than 200 Coresta units and most preferred porosities are usually inthe range of about 10 to 60 Coresta units. It is appreciated that thepaper/wrapper incorporating ceria/zirconia fibres may also be used as adouble or multiple wrap. A conventional cigarette filter may be attachedto the cigarette in the usual way, typically, having a length of about15 to about 35 mm.

The cigarettes of the present invention may be tailor made smokablecigarettes or may be made from the: non-smokable type of tobacco rod,such as described in Canadian Patent 1,235,039. According to one aspectof the invention, the non-smokable type is rendered smokable whencigarette paper/wrapper made from ceria/zirconia fibres are appliedthereto to form a smokable cigarette or the conventional cigarette paperis on the inside of the ceria/zirconia fibre paper/wrapper or tube andthe tobacco rod is inserted therein. The tobacco rods used may containconventional grades of tobacco, fillers, puffed tobacco and the like.

The ceria/zirconia fibre paper/wrapper may also comprise inert materialssuch as ceramics, clays and other suitable binders and sheetreinforcement materials.

To manufacture the cigarette paper/wrappers of the present invention,the ceria/zirconia fibre is preferably made into a sheet whereby thesheet may have a thickness normally in the range of about 0.04 mm up toabout 2 mm but preferably not exceeding about 1 mm in thickness. Thenovel sheet composition may be made by one or more standard continuouspapermaking processes such as that described in Canadian PatentApplication 2,323,126, directed to the incorporation of carbon fibres incigarette paper manufacture, and U.S. Pat. No. 4,915,117, directed tothe incorporation of ceramic fibres in cigarette paper manufacture, thesubject matter of such processes being incorporated herein by reference.The cigarette paper/wrappers, where the ceria/zirconia, fibres replaceconventional cigarette paper/wrapper fibres, are made by creating afibre suspension of ceria/zirconia fibres (typically, up to 65% byweight of ceria/zirconia fibres are used in the suspension) and otherconventional cigarette paper/wrapper fillers such as ceramics, clays andother suitable binders and sheet reinforcement materials. A viscositymodifier, such as an alginate, may also be added to the suspension toaid in the processing of the cigarette paper/wrapper by increasing theviscosity of the fibre suspension. To form the paper/wrapper, the fibresuspension may be spread out onto a screen or set of screens and driedto form a combustible paper/wrapper. The suspension may be further agedat an elevated temperature to evaporate any organics and develop,thereby, a porous non-combustible paper/wrapper.

As mentioned previously, the ceria/zirconia fibre can be used as areinforcement for conventional combustible cigarette paper/wrapperfibres. This can reduce the amount of conventional combustible cigarettepaper/wrapper fibres required. For instance, the fibre suspension mayinclude cellulosic fibres and is made as suggested above. Typically,about 30 to about 40% by weight of ceria/zirconia fibres, about 30 toabout 40% by weight of the combustible cigarette paper/wrapper fibres(ie. cellulosic fibres) and about 20 to about 40% by weight of theconventional cigarette paper/wrapper filler are used in the suspension.

In addition, it is known that cigarettes incorporate glass fibres intothe paper/wrapper as reinforcement material, for instance, as describedin U.S. Pat. No. 4,915,117. The glass fibres may be present in thecigarette paper/wrapper up to 35% by weight and, according to thepresent invention, the glass fibres are replaced with ceria/zirconiafibres using the method described above.

As taught in Applicant's International Patent Application WO 02/024005,herein incorporated by reference, various compositions are describedwith respect to sidestream smoke reduction. Those compositions typicallyinclude an oxygen storage and donor metal oxide oxidation catalyst andan essentially non-combustible finely divided porous adjunct for thecatalyst. Preferred oxygen storage and donor metal oxide oxidationcatalysts include rare earth metal oxides, particularly the lanthanideseries metal oxides. Cerium oxide is a preferred oxygen donor material.These sidestream smoke reducing compositions may be applied to thesurface of the cigarette paper/wrapper, may be incorporated into thecigarette wrapper/paper and/or impregnated into the cigarettewrapper/paper. When incorporating the composition into thepaper/wrapper, the wet strength of the paper material during manufacturelimits the amount of composition added. In accordance with the presentinvention, the use of ceria/zirconia fibres, and especially porousceria/zirconia fibres, to replace a portion or all of the cellulosefibres provides for an acceptable wet strength. By virtue of the presentinvention, loading of ceria as an active ingredient in the sidestreamsmoke composition can be increased to much higher levels than that whichcould be attained by incorporating the sidestream smoke composition intothe paper furnish. Furthermore, when higher loadings of ceria aredesired, the application of coatings containing ceria is not necessary.Since the porous ceria/zirconia fibres have sidestream smoke reductionproperties in some applications, the ceria/zirconia fibres may be allthat is needed in the paper, whereas in other applications, acombination of porous ceria/zirconia fibres and the sidestream smokereduction composition of our prior system may be required.

Other applications of the ceria/zirconia fibres include theincorporation of ceria/zirconia fibres into tobacco. Incorporation ofthe ceria/zirconia fibres may take place at any time prior to the finalpackaging of the tobacco product. In the case of cigarette tobacco, thefibres may be incorporated before or after blending of the varioustobaccos if, in fact, blended tobacco is employed. In addition, thefibres are dispersed throughout the treated tobacco and may be used inone or all of the blend constituents. The fibres facilitate processingof the tobacco and may enhance burn characteristics of the tobacco, suchas sidestream smoke reduction. Typically, the fibres are well dispersedthroughout the tobacco so that they will be uniformly effective duringthe entire period during which the composition is smoked.

The weight proportions of the components described above for use intobacco are usually within the following approximate weight ranges toprovide useful tobacco products. The amount of ceria/zirconia fibresadded to the tobacco may be about 1 to about 15% by weight, preferably,about 1% to about 10% by weight based upon the weight of the tobacco.

The tobacco may be further processed and formed into any desired shapeor used loosely (ie. cigars, cigarettes, and pipe tobacco) in a mannerwell-known to those skilled in the tobacco art. Other conventionaltobacco additive materials, such as flavourants and humectants may beused in the practice of the present invention without deviating from thescope thereof.

Other applications of the ceria/zirconia fibres include incorporation ofthe ceria/zirconia fibres into a filter. In one embodiment, theceria/zirconia fibres are placed in a cavity within the filter of thecigarette and sealed. The ceria/zirconia fibres may also be milled priorto placement within the cavity of the filter. Typically, the filtercavity length is approximately 4 mm. In another embodiment, conventionalfilter fibres, such as filter fibres described in Canadian Patents1,092,933; 1,301,012; and 2,177,496, are replaced either partially orwholly with ceria/zirconia fibres. Specifically, glass fibres incigarette filters, such as the filters described in U.S. Pat. No.5,829,449, are replaced with ceria/zirconia fibres.

In accordance with the present invention, at least one of the variouscigarette components of the present invention comprise ceria/zirconiafibres. For instance, the ceria/zirconia fibres may be used in severaldifferent combinations within a cigarette (ie. the cigarettepaper/wrapper and filter may comprise the ceria/zirconia fibres, whereasthe tobacco is conventional cigarette tobacco). All cigarette componentsmay comprise ceria/zirconia fibres.

Although preferred embodiments of the invention have been describedherein in detail, it will be understood by those skilled in the art thatvariations may be made thereto without departing from the spirit of theinvention or the scope of the appended claims.

1. A cigarette comprising a tobacco rod, a cigarette paper/wrapper forthe tobacco rod, and optionally a filter, wherein at least one of thetobacco rod, the cigarette paper/wrapper and the filter compriseceria/zirconia fibres.
 2. The cigarette of claim 1, wherein theceria/zirconia fibres are porous.
 3. The cigarette of claim 1, whereinthe ceria/zirconia fibres have a surface area in the range of about 1 toabout 200 m²/g.
 4. The cigarette of claim 1, wherein the ceria/zirconiafibres have a surface area less than about 1 m²/g.
 5. The cigarette ofclaim 1, wherein the cigarette paper/wrapper comprises porousceria/zirconia fibres.
 6. The cigarette of claim 1, wherein thecigarette paper/wrapper comprises ceria/zirconia fibres having a surfacearea greater than about 20 m²/g.
 7. The cigarette of claim 5, whereinthe cigarette paper/wrapper reduces sidestream smoke, the cigarettepaper/wrapper comprising a sidestream smoke reducing composition and theceria/zirconia fibres.
 8. The cigarette of claim 1, wherein theceria/zirconia fibres are made by fiberizing an aqueous solution of azirconium compound, ceria and a crystalline, colloidal zirconia sol; andheating the ceria/zirconia fibres to a temperature less than about 1100°C.
 9. The cigarette of claim 1, wherein the ceria/zirconia fibrescomprise up to about 50% by weight ceria.
 10. The cigarette of claim 1,wherein the tobacco rod comprises about 1 to about 15% by weight of theceria/zirconia fibres.
 11. The cigarette of claim 1 comprises thefilter.
 12. The cigarette of claim 11, wherein the filter comprises theceria/zirconia fibres.
 13. The cigarette of claim 12, wherein a cavitydefined in the filter comprises the ceria/zirconia fibres.
 14. Thecigarette of claim 12, wherein the filter comprises the ceria/zirconiafibres and conventional fibres.
 15. The cigarette of claim 1, whereinthe cigarette paper/wrapper comprises the ceria/zirconia fibres andconventional cigarette paper/wrapper fibres.
 16. The cigarette of claim1, wherein the cigarette paper/wrapper comprises up to 65% by weight ofthe ceria/zirconia fibres and at least 35% by weight of a conventionalcigarette paper/wrapper filler and/or conventional cigarettepaper/wrapper fibres.
 17. The cigarette of claim 16, wherein thecigarette paper/wrapper comprises about 30 to about 40% by weight of theceria/zirconia fibres, about 30 to about 40% by weight of theconventional cigarette paper/wrapper fibres and about 20 to about 40% byweight of the conventional cigarette paper/wrapper filler.
 18. Thecigarette of claim 15, wherein the conventional cigarette paper/wrapperfibres are cellulosic fibres.
 19. The cigarette of claim 16, wherein theconventional cigarette paper/wrapper filler is selected from the groupconsisting of a ceramic, a clay, a binder and a sheet reinforcementmaterial.
 20. The cigarette of claim 1 further comprising a conventionalcigarette paper between the tobacco rod and the cigarette paper/wrapper.